A Tour of the Cell Microscopic view Membrane structure Nucleus and ribosomes The Endomembrane System Chloroplasts, Mitochondria Cytoskeleton Cilia and flagella

A Prokaryote Measured in microns ~ 0.5  m Example?Bacteria Name some structures: Flagella Pili Ribosomes (blue ‘dots’) Capsule Cell wall Plasma membrane orange green yellow Nucleoid region (DNA)

Functions? 1. Surface appendages that allow a bacterium to stick to a surface 2. Where are proteins synthesized? 3. The sticky, jellylike protective layer outside the cell wall 4. The rigid structure that surrounds, supports, and protects the cell 5. Which structure is a selective barrier, allows passage of oxygen, nutrients, and wastes? 6. Where is the cell's DNA, containing the genes that control the cell 7. The structure that propels the cell Flagella Plasma membrane Ribosomes Pili Cell wall Capsule Nucleoid region

Compare cells 1. Which is the animal cell? 2. Which is the plant cell? 3. Which is characteristic of bacteria? 4. Which does not have a nucleus? 5. Which does not have a cell wall? 6. Which does not have organelles? A B C

Eukaryotic cells Plasma membrane Nucleus Ribosomes Endoplasmic Reticulum (rough, smooth) Cytoskeleton The Golgi Apparatus Lysosomes Mitochondria DNA Cilia, flagella

Plasma membrane Separates living cells from nonliving surroundings It is known as? the fluid mosaic model Cholesterol Lipid bilayer Cytoskeleton Protein Cytoplasm Extracellular fluid Carb Glycoprotein

Phospholipid bilayer Hydrophilic ‘head’ Hydrophilic ‘tails’ Hydrophilic ‘head’ Extracellular fluid Cytoplasm ? ? ? What is the function of this component?

Learning check Which best describes the structure of the plasma membrane? a.Proteins sandwiched between 2 layers of phospholipid b.Proteins embedded in 2 layers of phospholipid c.A layer of protein coating a layer of phospholipid d.Phospholipids embedded in 2 layers of protein

The Nucleus Is the ‘manager’ of the cell What does it contain? DNA (Chromatin; chromosomes) Nucleolus (Produces parts of ribosomes) It is bordered by a double membrane & has pores

What is chromatin? Long DNA molecules + protein (forms long fibers) What is the nucleolus? Ball like mass (of fibers and granules) Produces part of ribosomes (blue ‘dot’)

What are ribosomes? Organelles responsible for protein synthesis Where do they go? Move from nucleus to cytoplasm Why? Protein synthesis occurs in the cytoplasm

Recall protein synthesis? (cf last talk on molecules of life) DNA Transfers information To mRNA Leaves nucleus Travels to cytoplasm Binds to ribosome Protein synthesized

Learning check In eukaryotic cells, the first step in protein synthesis is the ____. a.translation of an RNA nucleotide sequence into a sequence of amino acids b.linking of nucleotides to form a polypeptide c.translation of a DNA nucleotide sequence into a sequence of amino acids d.transferring of information from DNA to messenger RNA

Endoplasmic reticulum RER: Makes membrane and secretory proteins SER: lipid synthesis and detoxification SER RER with ribosomes Nuclear membrane (blue ‘dots’)

Secretory proteins After the RER synthesizes a molecule, it packages the molecule into transport vesicles Example? Saliva with enzymes Ribosome with peptide chain Secretory vesicle Buds off

SER No ribosomes Structure? But, membrane has many enzymes What are some of the enzyme functions? Ovaries, testes:Sex hormones enriched Liver cells:Detoxification of drugs

Learning check Proteins destined for secretion are made on _____ bound to the _____. a. lysosomes... Golgi apparatus b. ribosomes... Golgi apparatus c. ribosomes... mitochondria d. mitochondria... endoplasmic reticulum e. ribosomes... endoplasmic reticulum

The Golgi Apparatus Refines ER products and packages And packages them in transport vesicles transport to organelles Flattened sacs vesicles ‘become’ lysosomes export from cells What do transport vesicles do?

Lysosomes Membrane enclosed sac of digestive enzymes Food What do they break down? Damaged organelles Proteins, polysaccharides, fats, nucleic acids Mitochondria Lysosome

Learning check Lysosomes can form by budding directly off _____. a.the Golgi apparatus b.the endoplasmic reticulum c.mitochondria d.chloroplasts e.the nucleus

The Endomembrane System Transport of ? Digestive ? Storage ? Secreted ?

Chloroplasts & Mitochondria Think energy! Site of photosynthesis Site of cell respiration Conversion of light (energy) to chemical energy More to come in Chapter 7 Produces ATP (energy) from food molecules More to come in Chapter 6

Cytoskeleton Its like an infrastructure: ‘Skeleton’ ‘Muscles’ What is it made up of? Its a network of fibers (microtubules, filaments)

Microtubules Are straight, hollow tubes What are they composed of? Globular proteins Tubulin What are some functions? Anchor organelles Move organelles Guide movement of chromosomes Crawling motion

Rapid degeneration and rebuilding of microtubules Crawling motion? Allows ‘crawling’ movement like the amoeba And some of our white blood cells

Cilia and flagella are motile appendages How do cilia move? In a coordinated back-and-forth way Paramecium Example?

How do flagella move? In a whip-like motion Sperm Example?

What happens in our respiratory tract? The human windpipe is lined with cilia on non- motile cells Function to move fluid over the surface of the tissue Sweep mucus with trapped debris out of lungs

Learning check Which one of the following statements about cilia and flagella is true? a.Cilia and flagella are typically found just inside a cell membrane. b.Cilia are typically much longer than flagella. c.Flagella and cilia assist in moving a cell or the cell's surroundings. d.The inside of flagella and cilia consists of many rows of actin and myosin filaments. e.Cilia are only found in animals.

Which of these organelles is found within the nucleus? a. nucleolus b. mitochondrion c. SER d. chloroplast e. ribosome Which of these organelles carries out cellular respiration? a. nucleolus b. chromatin c. SER d. mitochondrion e. ribosome Which organelle plays a role in intracellular digestion? a. Lysosome b. ribosome c. chloroplast d. Golgi apparatus

Concept Check The three domains of life described by biologists today include the bacteria, the archaea and the eukarya (all other forms of life). A.The prokaryotes do not have a plasma membrane surrounding the cell. B.The prokaryotes use RNA and not DNA to pass on the genetic message. C.The eukaryotes have the interior of the cell divided by internal membranes into specialized compartments. D.The eukaryotes engage in cellular metabolism while the prokaryotes do not.